Dont think its a Kingswood

[HK1837]

For starters if it is a Kingswood it isn't a Sandman, there were no KIngswood Sandman panel vans. ID tags is a good start.

[ABSINTH74HQ]

I'm going through the same dilema right now with my HQ, the body is stuffed, I will attempt to save it , but if beyond repair, I'll do a shell swap.
I think the integrity is still there especially if tags chassis and eng no still match! Yes the value may be degraded slightly, but she's still a Sand man in my eyes.
Byron, HK1837 is the guru of this stuff, and will be able to tell you with a degree of certainty what you have, and what colours it should be, what eng no you should have, all from the details on the tags.
His info has been a god send to me!

Cheers, Scotty.